Methods for producing single crystal samples using atmospheric gases whose oxygen partial pressure is controlled using electrochemical oxygen pumps comprising solid electrolytes are known. Specifically, in these techniques, long, cylindrical solid electrolytes are sealed at both ends and provided with net-like platinum electrodes on portions of both the inner and outer surfaces of the cylinder's periphery. In using the sealed cylindrical solid electrolytes as oxygen pumps, inert gas is supplied into the solid electrolyte and a voltage is applied to both electrodes, which removes oxygen from within the aforementioned inert gas to the outside of the solid electrolyte and reduces the partial pressure of oxygen in the inert gas (see Patent Document 1).
The present inventors further propose improved techniques in which, as a mechanism for recycling waste gas, a conductance means and exhaust-speed varying means are installed in a return path from a sample producing apparatus. Further, the present inventors propose that by maintaining a positive pressure in the oxygen pump, contamination resulting from mixture with external gases or the like is prevented (see the specification and drawings attached to Japanese Patent Application No. 2003-42403).
Oxygen pumps which comprise solid electrolyte materials such as strontium-doped lanthanium manganate and which comprise cylindrical structures such as honeycomb structures are also known, where such oxygen pumps produce atmospheric gases with oxygen pressures ranging from high to very-low, preventing damage using feedback control of operational voltage and the like on the basis of oxygen partial pressure values from a sensor (see Patent Document 2).
Floating zone apparatuses in which a number of gas supply circuits are connected in parallel are known, where each circuit is provided with a mass flow controller such that the atmosphere can be varied over a wide range in order to adjust to variations in vapor pressure (see Patent Document 3).
Methods are also known which reuse electrochemical oxygen sensors that monitor exhaust gases from internal engines, by applying a voltage equal to or greater than a saturation voltage (see Patent Document 4).    [Patent Document 1] Japanese Patent Application Kokai Publication No. (JP-A) 2002-326887 (unexamined, published Japanese patent application).    [Patent Document 2] Japanese Patent Kohyo Publication No. (JP-A) H10-500450 (unexamined Japanese national phase publication corresponding to a non-Japanese international publication).    [Patent Document 3] Japanese Patent Application Kokai Publication No. (JP-A) 2001-114589 (unexamined, published Japanese patent application).    [Patent Document 4] Japanese Patent Kohyo Publication No. (JP-A) 2003-510588 (unexamined Japanese national phase publication corresponding to a non-Japanese international publication).